Bidens cernua

Nodding Bur Marigold

Nodding Bur Marigold
Photo courtesy Brousseau Collection

Flora, fauna, earth, and sky...
The natural history of the northwoods

Name:

• Bidens, from the Latin, bidens, "with two prongs, points", a reference to the prominent prongs on the seeds.
• cernua, from the Latin, cernuus, "inclining the head, stooping"; hence "nodding"
• Common name from tendancy of mature flowers to droop, the clinging nature of the seed (those Bidens seeds with two prongs), and the superficial resemblance of the yellow flower to the marigold.
• Other common names include: Sticktight, Nodding Beggar's Ticks, Nodding Beggarsticks, Nikkende Brøndsel (Den), Nuokkurusokki (Fin), Sgeachag Moire (Gaelic), Nickender Zweizahn (Ger), Nikkebrønsle (Nor), Dvojzub Ovisnutý (Slovak), Nickskära (Swe)
• Another name for beggarticks is stick-tights. Walking through a stand of these plants in late summer or autumn results in numerous barbed nutlets adhering to clothing.

Taxonomy:

• Kingdom Plantae, the Plants
  • Division Magnoliophyta, the Angiosperms (flowering plants)
    • Class Magnoliopsida, the Dicotyledons
    • Subclass Asteridae
      • Order Asterales, the Sunflowers
        • Family Asteraceae, the Sunflowers
          • Genus Bidens, the Bur Marigolds
• Taxonomic Serial Number: 35710

Description:

• Annual swamp or bog plant
• Leaves opposite, simple, linear to lanceolate, pointed at the tip, more or less rounded at the sessile or slightly clasping base, with or without teeth, smooth or hairy, up to 6" long, up to 1½" wide.
• Stem erect or sometimes growing along the ground and rooting at the nodes, smooth or hairy, often branched, up to 5' tall.
• Root a taproot
• Flowers many, crowded together into a head, the outer yellow and flat, the inner yellow and tubular, forming a disk, with several heads per plant, each head subtended by 5-8 narrow, leafy bracts.
  • Sepals absent.
  • Petals yellow; some united to form flat rays up to 2/3" long and 1/3" wide, others yellow, 5-lobed, united below into a tube.
  • Stamens 5
  • Ovary inferior (below flower)
• Fruit an achene, mostly flat, broadest at top, tapering to a narrow base, green-black, barbed along the edge, up to 1/3" long, about 1/10" broad, with four stiff barbed awns at the upper end.
• Flowers August-October.
• Flower heads are erect, but then become nodding with age.

Identification:

• A waterside plant
• Distinguished from other species by its undivided simple leaves, its nodding heads, and its somewhat winged fruits.
• Field Marks
  • showy yellow rays
  • undivided simple leaves

Distribution:

• New Brunswick to British Columbia, south to North Carolina, Oklahoma, New Mexico, and California. Also Eurasia
• Known from St. Louis and Cook Counties in the Minnesota Arrowhead.

Habitat:

• Around ponds and lakes, along streams, swamps, wet meadows, roadside ditches, marshes, bogs, and in areas of disturbed, wet soils.

Associates:

• Trees: Tammarack (Larix laricina), Black Spruce (Picea mariana)
• Shrubs: Bog Birch (Betula pumila), Leatherleaf (Chamaedaphne calyculata), Sweet Gale (Myrica gale)
• Herbs: Blue Flag Iris (Iris versicolor), Cattails (Typha spp)
• Ground Covers: Sphagnum Mosses (Sphagnum spp.)
• Mammals: Moose (Alces alces)
• Birds: Fruits eaten by ducks.

History:

Uses:

Reproduction:

• Reproduces by seed
• Flowers July to October

Propagation:

• By seed

Cultivation:

• Hardy to USDA Zone 3 (average minimum annual temperature -40ºF)
• Though rarely sown in water and bog gardens, it often appears there by natural means.

Links:

• Den Virtuella Floren, Naturhistoriska riksmuseet, Stockholm

Comments:

• One of five species of Bidens known to occur in northeastern Minnesota. Others include Beck's Water Marigold (Bidens beckii), Purple Stemmed Beggarticks (Bidens connata), Small Beggarticks (Bidens discoidea), and Devil's Beggarticks (Bidens frondosa).